Last month’s 118 fatalities – more than one in six of whom were unarmed – reversed a downward trend over the previous four months

July was the deadliest month of 2015 so far for killings by police after registering 118 fatalities, according to the Guardian’s ongoing investigation The Counted, which now projects that US law enforcement is on course to kill more than 1,150 people this year.

The July figure brought an end to a steady decline in totals over the previous four months. After 113 people were killed in March, 101 died in April, 87 fatalities were recorded in May and 78 in June.

At least 20 people killed in July – more than one in six – were unarmed, including Samuel DuBose, who was shot by University of Cincinnati officer Ray Tensing in a 19 July traffic stop that has become the latest flashpoint in protests over the police’s use of deadly force.

Of the 118 people, 106 died from gunfire, making July also the first month of 2015 in which that number has exceeded 100. Two people died after officers shocked them with Tasers, two died being struck by police vehicles, and eight died after altercations in police custody.

The Counted is recording every killing by police in the US this year because the federal government does not currently publish a comprehensive database. Instead the FBI runs a voluntary program in which agencies may submit numbers of “justifiable homicides”.

Tensing had claimed DuBose dragged him with his car, but footage recorded by Tensing’s body camera refuted his account. The officer was charged with murder on Wednesday, when at a press conference the Cincinnati prosecutor Joe Deters called the shooting “senseless” and said Tensing “should never have been a police officer”.

Tensing, who turned himself in on Wednesday, was arraigned on Thursday and has been released on bail. On Friday it was announced by Deters’s office that two officers who appeared to reinforce Tensing’s false account will not be charged with any crimes.

As in the DuBose case, police in Seneca, South Carolina, who fatally shot 19-year-old Zachary Hammond said he tried to use his vehicle as a weapon. The officer who shot Hammond was assisting an undercover drugs investigation and said Hammond drove his car at the officer to evade a stop. An attorney for Hammond’s family has since rejected this claim, citing autopsy results that he said indicated Hammond was shot from behind and his car was not moving.

In Mississippi, investigators said 39-year-old Jonathan Sanders died from “manual asphyxiation” after an altercation with Stonewall police officer Kevin Herrington. According to the Sanders family’s attorneys, Sanders repeatedly told Herrington “I can’t breathe” while the officer applied a chokehold that witnesses said lasted more than 20 minutes. An earlier suggestion by Sanders’s own attorney that the officer used a flashlight to execute the hold, was denied by Stonewall’s police chief, who described the incident as “a fight”.

Across the state, in Olive Branch, Mississippi, 30-year-old Troy Goode died after being “hogtied” by Southaven police when he started “acting strange” while returning from a concert in Memphis. It is believed Goode was under the influence of LSD, authorities said. An attorney for Goode’s family told the Guardian that when they called the hospital to try to visit Goode, authorities told them they would be arrested if they arrived.

The Guardian’s total does not include a number of other deaths in police custody that have been increasingly discussed following the death of 28-year-old Sandra Bland at a jail in Waller County, Texas. The Counted does not record deaths in custody without clear evidence or official accounting of a physical altercation or other direct action of law enforcement that could reasonably be seen to have caused the death.

In July, at least eight women, five of whom were black, died in US jails. Despite the increased attention on the issue, the phenomenon does not appear to be on the rise. The Bureau of Justice Statistics said that according to data collected from 2000 to 2012, about 10 women die in the custody of local jails every month.