(CNN) Baltimore is seeing its deadliest month in 15 years after an outbreak of Memorial Day weekend violence left nine people dead in 29 shootings.

So far, Baltimore has tallied 35 homicides this month, police said.

The last time Baltimore saw that many homicides was December 1999, police said.

The only month to surpass 35 homicides was the prior month, November 1999, when 36 homicides were recorded, according to police statistics since 1999. That year was also Baltimore's deadliest in the past 16 with 305 homicides, police figures show.

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Council member Mary Pat Clarke believes this month's violence is a legacy of the riots and unrest over the death of Freddie Gray after being in police custody in April

The riots triggered fires and looting in April, and at least 20 officers were injured in the melee. Gov. Larry Hogan declared a state of emergency and dispatched the National Guard to address the unrest.

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"It was an earthquake kind of time, and I think we're still dealing with the aftershock," Clarke said, according to CNN affiliate WJZ

Are police staging a work slowdown?

The latest homicide statistics arrive amid reports that Baltimore police officers have lost confidence in the chain of command and that officers have coordinated a work slowdown by not talking to community members and showing less initiative. The drops in arrests and increase in murders are the result of officers refusing to follow their marching orders, according to one Baltimore officer who spoke with CNN.

Photos: Baltimore protests Photos: Baltimore protests People hold hands during a rally at Baltimore City Hall on Sunday, May 3. The death of Freddie Gray, who died in police custody, sparked rioting in Baltimore and protests across the country Hide Caption 1 of 68 Photos: Baltimore protests Members of the National Guard board a truck at an armory staging area on May 3 in Baltimore. After a night of relatively peaceful protests, the city lifted a curfew , the National Guard is preparing its exit and a mall that had been a flashpoint in the protests has been reopened. Hide Caption 2 of 68 Photos: Baltimore protests Medics take a man away after police pepper-sprayed him on Saturday, May 2, in Baltimore's Sandtown neighborhood where Freddie Gray was arrested in April. Hide Caption 3 of 68 Photos: Baltimore protests Police detain a man on May 2 in Baltimore's Sandtown neighborhood. Hide Caption 4 of 68 Photos: Baltimore protests Protesters hold signs on May 2 in the Sandtown neighborhood. Hide Caption 5 of 68 Photos: Baltimore protests Protesters march from the Gilmor Homes housing community, where Freddie Gray was arrested, to City Hall on Saturday, May 2, in Baltimore. Hide Caption 6 of 68 Photos: Baltimore protests Police in riot gear enforce a 10 p.m. curfew and clear Baltimore streets of protesters and media on Friday, May 1. Hide Caption 7 of 68 Photos: Baltimore protests U.S. Rep. Elijah Cummings, D-Maryland, helps clear Baltimore streets of protesters on May 1. Hide Caption 8 of 68 Photos: Baltimore protests Demonstrators celebrate the announcement that six officers were charged May 1 in Gray's death. Hide Caption 9 of 68 Photos: Baltimore protests Demonstrators march through the streets of Baltimore after the charges against the officers were announced May 1. Hide Caption 10 of 68 Photos: Baltimore protests Police on horseback block a Baltimore street on May 1. Hide Caption 11 of 68 Photos: Baltimore protests A demonstrator celebrates in Baltimore the charges were announced on May 1. Hide Caption 12 of 68 Photos: Baltimore protests A member of the National Guard stands outside Baltimore City Hall as protesters gather on Wednesday, April 29. Hide Caption 13 of 68 Photos: Baltimore protests High school and college students march from Baltimore's Penn Station to City Hall on April 29. Hide Caption 14 of 68 Photos: Baltimore protests A community organizer later identified as Joseph Kent paces in front of riot police with his hands up during a curfew in Baltimore on Tuesday, April 28. Moments later, he was seen being arrested by police live on CNN . Kent's lawyer said on April 30 that his client had been released from jail. While some protesters defied the curfew and faced off with police, demonstrations Tuesday were largely peaceful. Hide Caption 15 of 68 Photos: Baltimore protests State Sen. Catherine E. Pugh embraces a protester while urging the crowd to disperse ahead of the 10 p.m. curfew. Hide Caption 16 of 68 Photos: Baltimore protests People attempt to stop protesters from approaching a police line on April 28. Hide Caption 17 of 68 Photos: Baltimore protests A Baltimore police captain tries to calm a protester on April 28. Hide Caption 18 of 68 Photos: Baltimore protests Two women sweep up the streets in Baltimore -- reflected in the broken window of a storefront on April 28. See more photos of the cleanup efforts. Hide Caption 19 of 68 Photos: Baltimore protests A band plays music during protests on April 28 in Baltimore. Hide Caption 20 of 68 Photos: Baltimore protests A boy in Baltimore offers water to a police officer on April 28. Hide Caption 21 of 68 Photos: Baltimore protests Jerrie Mckenny, left, and her sister Tia Sexton embrace as demonstrators hold hands and sing the hymn "Amazing Grace" in Baltimore on April 28. Hide Caption 22 of 68 Photos: Baltimore protests Demonstrators stand in front of a police line and call for peace after a bottle was thrown on April 28. Hide Caption 23 of 68 Photos: Baltimore protests Maryland National Guardsmen patrol the streets on April 28. Hide Caption 24 of 68 Photos: Baltimore protests The remains of a senior center smolder on April 28. Riots broke out Monday, April 27, after Freddie Gray's funeral Hide Caption 25 of 68 Photos: Baltimore protests Police retreat from burned-out cars in an intersection on Monday, April 27. Hide Caption 26 of 68 Photos: Baltimore protests Firefighters respond to a burning building during the riots late April 27. Hide Caption 27 of 68 Photos: Baltimore protests A police officer walks by a burning building on April 27. Hide Caption 28 of 68 Photos: Baltimore protests Police stand guard on April 27. Hide Caption 29 of 68 Photos: Baltimore protests Protesters climb on a destroyed Baltimore Police car in the street near the corner of Pennsylvania and North avenues on April 27. Hide Caption 30 of 68 Photos: Baltimore protests A mixture of milk and water rolls down a man's chest after he was pepper sprayed by the Baltimore Police April 27. Hide Caption 31 of 68 Photos: Baltimore protests A man rides a bicycle through heavy smoke emitting from a nearby store on fire April 27. Hide Caption 32 of 68 Photos: Baltimore protests A man shouts for calm as protesters clash with police April 27. Hide Caption 33 of 68 Photos: Baltimore protests Police carry an injured officer from the streets near Mondawmin Mall in Baltimore on April 27. Hide Caption 34 of 68 Photos: Baltimore protests People carrying goods leave a CVS pharmacy near Pennsylvania and North avenues on April 27. Hide Caption 35 of 68 Photos: Baltimore protests A demonstrator raises his fist as police stand in formation on April 27. Hide Caption 36 of 68 Photos: Baltimore protests Armored cars drive down Pennsylvania Avenue as looters break into shops on April 27. Hide Caption 37 of 68 Photos: Baltimore protests People lock arms and form a line opposing police at the corner of Pennsylvania and North avenues on April 27. Hide Caption 38 of 68 Photos: Baltimore protests Police form a barrier between protesters and a burning CVS being attended to by firefighters on April 27. Hide Caption 39 of 68 Photos: Baltimore protests People carry goods out of a CVS pharmacy on April 27. Hide Caption 40 of 68 Photos: Baltimore protests A police vehicle burns April 27. Hide Caption 41 of 68 Photos: Baltimore protests A police officer throws an object at protesters on April 27. Hide Caption 42 of 68 Photos: Baltimore protests A man carries items from a store as police vehicles burn on April 27. Hide Caption 43 of 68 Photos: Baltimore protests A police officer checks on a man who was injured on April 27. Hide Caption 44 of 68 Photos: Baltimore protests A police officer is carried to safety after being hit in the head with a rock during the riot on April 27. Hide Caption 45 of 68 Photos: Baltimore protests A police officer uses pepper spray on rioters on April 27. Hide Caption 46 of 68 Photos: Baltimore protests Police officers push back a protester on April 27. Hide Caption 47 of 68 Photos: Baltimore protests Police react during the riot on April 27. Hide Caption 48 of 68 Photos: Baltimore protests Baltimore police officers in riot gear look toward protesters near Mondawmin Mall on April 27. Hide Caption 49 of 68 Photos: Baltimore protests Baltimore Police Commissioner Anthony Batts chases away protesters in a parking lot on April 27. Hide Caption 50 of 68 Photos: Baltimore protests A woman abandons her car in the middle of an intersection as Baltimore Police officers clash with protesters outside the Mondawmin Mall in Baltimore on April 27. Hide Caption 51 of 68 Photos: Baltimore protests Police handle the protesters during a riot on April 27. Hide Caption 52 of 68 Photos: Baltimore protests A demonstrator taunts police on April 27. Hide Caption 53 of 68 Photos: Baltimore protests Protesters stand off with police during a march in honor of Gray in Baltimore on Saturday, April 25. Hide Caption 54 of 68 Photos: Baltimore protests A protester throws a barricade at a bar near Oriole Park at Camden Yards after a rally on April 25. Hide Caption 55 of 68 Photos: Baltimore protests Protesters chase after a car as it drives in reverse after the rally on April 25. Hide Caption 56 of 68 Photos: Baltimore protests A protester breaks a store window after the rally in Baltimore on April 25. Hide Caption 57 of 68 Photos: Baltimore protests Protesters get into a shoving match with police during a march downtown on April 25. Hide Caption 58 of 68 Photos: Baltimore protests Protesters and police square off April 25. Hide Caption 59 of 68 Photos: Baltimore protests Protesters drive through the Camden Yards area on April 25. Hide Caption 60 of 68 Photos: Baltimore protests Members of the Baltimore Police Department stand guard Thursday, April 23, outside the department's Western District station during a protest. Hide Caption 61 of 68 Photos: Baltimore protests A police officer films protesters from the steps of the Western District station on April 23. Hide Caption 62 of 68 Photos: Baltimore protests Empowerment Temple Pastor Jamal Harrison Bryant speaks in front of City Hall in Baltimore on April 23. Hide Caption 63 of 68 Photos: Baltimore protests Demonstrators put their fists in the air during a protest outside the Baltimore police's Western District station on Wednesday, April 22. Hide Caption 64 of 68 Photos: Baltimore protests Hundreds of demonstrators march toward the Western District station on April 22. Hide Caption 65 of 68 Photos: Baltimore protests People march through the streets of Baltimore on April 22. Hide Caption 66 of 68 Photos: Baltimore protests Demonstrators argue with Baltimore officers during the protest on April 22. Hide Caption 67 of 68 Photos: Baltimore protests A woman is comforted during the protest on April 22. Hide Caption 68 of 68

Last week, a Baltimore grand jury indicted six officers in the case of Gray, who was arrested on a weapons charge on April 12 but suffered a severe spinal cord injury in police custody that led to his death seven days later. Police took Gray into custody by putting him into a transport van, and police have acknowledged that Gray wasn't buckled into a seat belt while being transported.

The officers face a range of charges from involuntary manslaughter to reckless endangerment, but the driver of the transport van, Caesar Goodman, will face the most severe charge of second-degree depraved heart murder.

In a interview with CNN earlier this month, Police Commissioner Anthony Batts attributed the spike in murders to additional gang violence, not a slowdown.

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"I hope that there is not a slowdown and what kind of message that sends to the community and to the government if that's the case," Batts said.

The numbers are up, Batts said, because "multiple people" have been "shot in groupings ... leading us to believe there is a gang nexus to the shootings that have taken place."

'We can't tolerate this'

Mayor Stephanie Rawlings-Blake found the trend distressing and said additional police would be sent to communities with the most crime.

The mayor held an emergency meeting Sunday with police commissioner and command staff to address escalating violence, the station reported.

"We can't tolerate this ... on any level," the mayor said, according to the outlet. "My hope is the police will have the support they need from the community to be able to get some answers and bring some of these individual(s) to justice."

Police Commissioner Batts said getting answers and community help won't be easy, the station reported.

"We can't demand that of citizens. We have to go out and earn their trust," Batts said, according to the affiliate.

'Tragedy unfolding in our backyard'

Cornell William Brooks, president and CEO of NAACP, said the community and the police need to work together to reduce the violence. The NAACP, a civil rights group, is headquartered in Baltimore.

"Well, this is a tragedy unfolding in our backyard, the hometown of the NAACP," Brooks said. "We don't know why we see this horrific spike in murders and shootings.

"There is no excuse, none whatsoever for any kind of slow down or work stoppage," Brooks said. "The officers have taken an oath, and that oath is not to be abdicated."

Photos: Cleaning up after Baltimore riots Photos: Cleaning up after Baltimore riots People help clean up a CVS pharmacy in Baltimore on Tuesday, April 28, the morning after riots broke out during protests on Monday, April 27. The unrest followed the funeral for Freddie Gray , who died of a severe spinal cord injury he got while in police custody. There were more than 230 arrests, 144 vehicle fires and 15 structure fires, a city official said. Hide Caption 1 of 13 Photos: Cleaning up after Baltimore riots Members of the community clean up debris on April 28 from the CVS that was burned and looted in the riots. Hide Caption 2 of 13 Photos: Cleaning up after Baltimore riots A neighborhood cleanup crew works to clear trash from the streets on April 28. Hide Caption 3 of 13 Photos: Cleaning up after Baltimore riots Caroline Byrd helps with cleanup efforts on April 28. Hide Caption 4 of 13 Photos: Cleaning up after Baltimore riots Volunteers help clear trash from a looted business on April 28. Hide Caption 5 of 13 Photos: Cleaning up after Baltimore riots A man sweeps the street as law enforcement officers stand guard on April 28. Hide Caption 6 of 13 Photos: Cleaning up after Baltimore riots Baltimore firefighters inspect a burned store on April 28. Hide Caption 7 of 13 Photos: Cleaning up after Baltimore riots People helping clean debris are seen in the reflection of a broken window on April 28. Hide Caption 8 of 13 Photos: Cleaning up after Baltimore riots Jason Park, left, and business owner Sung Kang survey the damage to his store on April 28. Hide Caption 9 of 13 Photos: Cleaning up after Baltimore riots Men wearing work gloves help clear debris on April 28. Hide Caption 10 of 13 Photos: Cleaning up after Baltimore riots Kailah Johnson, 5, joins her mother in a neighborhood cleanup on April 28. Schools were closed across the city. Hide Caption 11 of 13 Photos: Cleaning up after Baltimore riots Volunteers help clear the wreckage from damaged stores on April 28. Hide Caption 12 of 13 Photos: Cleaning up after Baltimore riots Employee Sam Wirtz, left, surveys the damage to his store that came during the unrest on Monday, April 27. Hide Caption 13 of 13

But CNN law enforcement analyst Tom Fuentes said officers may be thinking twice about taking risks and showing aggressive policing in the wake of prosecutors filing charges against so many officers in the Gray case.

"These are legitimate concerns that the police have of being backed, trying to stop these murders that are in the streets," said Fuentes, a former FBI assistant director.

He also urged the community and police to engage in a discussion about public safety.

"This is a crisis that's being manufactured, I think, by the fact the community is not supporting the police," Fuentes said.

Overall this year, police report that Baltimore's homicides amount to 108 so far this year, compared with 79 at the end of May 2014, police figures show. There have also been 205 nonfatal shootings so far this year, compared with last year's figure of 115, the affiliate said.