(CNN) More arrests are expected in connection with the deaths of a dozen residents at a Florida nursing home, a police spokesman said Tuesday.

The investigation into the deaths of 12 people at the Rehabilitation Center at Hollywood Hills in Hollywood, Florida, remains "ongoing," said Hollywood Police Chief Chris O'Brien.

The residents -- aged from 71 to 99 -- died within days of a power outage due to Hurricane Irma in September 2017.

The Medical Examiner has ruled their deaths "homicides resulting from heat exposure due to environmental issues," according to a police fact sheet

Police on Tuesday said four people connected to the Rehabilitation Center had been arrested . "The Hollywood Police Department remains diligent in investigating all aspects of this case and additional arrests are anticipated," O'Brien said.

Felony charges

All four defendants appeared in court Tuesday.

Jorge Carballo

Jorge Carballo, the facility administrator, and Sergo Colin, night shift nursing supervisor, were each charged with 12 counts of aggravated manslaughter. A first degree felony, manslaughter occurs when someone causes a death due to negligence and in this case the charge is "aggravated" because the victims were elderly or incapable adults, police said.

Sergo Colin

The two defendants wore tan jumpsuits and held their hands cuffed in front of them. At one point, Carballo appeared to be wiping tears from his eyes. Carballo and Colin had their bonds set at $90,000 total, $7,500.00 for each count.

Tamika Tory Miller

Tamika Miller, a licensed practical nurse, faces six counts of aggravated manslaughter and three counts of tampering with evidence in connection with patient medical records, considered a third degree felony. Her bail had not been set early Tuesday.

Althia Kenesha Meggie

Althia Meggie, a registered nurse, faces two counts of aggravated manslaughter and two counts of tampering with evidence in connection with patient medical records. Bond for Meggie was set at $17,000.

"The four individual's now facing criminal charges failed to take the actions needed to protect their patients and render aid at a time when they needed it the most," said O'Brien at Tuesday's news conference.

Defense

A lawyers for one of the defendants noted that his client requested help during the storm.

David Frankel, a lawyer Colin, emphasized at a Monday news conference that the nursing home staff had reached out for assistance.

"These people, did everything they could. They were calling for emergency help. They were promised they were going to get help and they were abandoned," said Frankel.

Jim Cobb, an attorney who represents Carballo, told CNN "They did their jobs to the best of their ability in a natural disaster emergency."

Attorney Lawrence Hashish said Meggie, who was working as a temp at Rehabilitation Center, was filling in for one day on the night shift during the aftermath of Hurricane Irma. He said that he does not believe his client should be blamed for the deaths.

O'Brien holds the opposite view. He said the four defendants "neglected their duties and failed to provide adequate care."

"These are trained professionals who should have been aware of the environmental hazards in the facility and they chose to ignore them," he said.

Families of the victims

Pedro Franco, son of two of the victims, Miguel Franco, 93, and Cecilia Franco, 90, told CNN's Alisyn Camerota on Tuesday that all the defendants needed to do was call 911.

"These are people who were trained to take care of cases like this," said Franco. "They never had consideration for all the people that died even though they say they did but they didn't. Because with just one simple phone call they would have taken care of this but that didn't happen."

Franco's lawyer, Albert Levin, told Camerota that the defendants could have transferred the patients to a fully functioning hospital situated "literally 100 yards across a parking lot" from the nursing home. He added that if it is proven that the defendants falsified documents, then "what that shows is a consciousness of guilt, and that's a real problem."

Hurricane Irma

Hurricane Irma made landfall in Florida on Sunday, September 10, 2017. Storm damage knocked out the air conditioning system in the nursing home and the residents of the home suffered in the heat for days.

On Wednesday, officials first learned that the patients had experienced hazardous heat conditions -- but by then, eight residents had been confirmed dead. Three more residents died the following week, and a 57-year-old woman died one week after that.

The nursing home's license has since been revoked and the facility has been ordered to pay administrative fines and prosecutorial costs.

In the days following the deaths, Gov. Rick Scott set new emergency requirements for the state's nursing homes.

Nursing homes and assisted-living facilities must have supplies, power and resources, including a generator and adequate fuel, to sustain operations and maintain a comfortable temperature for at least 96 hours after a power outage, under the new mandate.

Currently, 25 of 687 licensed nursing homes do not have a fully approved, implemented emergency power plan or a variance, according to the Florida Agency for Health Care Administration. Only 279 facilities have approved and implemented plans.

Some 383 facilities currently have only variances allowing them additional time to fully implement their action programs.