Chicago saw a dramatic spike in the number of homicides and shootings in January — the bloodiest start to a year in at least 16 years and a blow to a police force struggling to regain public trust following the release of a video of a white officer fatally shooting a black teen.

In a news release Monday, Chicago police reported that 51 homicides were committed in the city last month, compared with 29 in January 2015. The number of shooting incidents more than doubled, from 119 last January to 242 this January. The number of shooting victims increased from 136 to 292.

"We can't put our finger on" specific reasons for the increase, the city's interim police superintendent, John Escalante said. But he noted the increase coincides with an equally dramatic decrease in the number of street stops made in January. He said a policy change that went into effect in this year requires officers to fill out lengthier forms than the brief "contact cards" they used through 2015 and that officers are going through training now to help them deal with the new forms.

Escalante also said officers have expressed concerns "about being the next viral video. Even when they're doing something right, they're concerned that their actions will be questioned and they will be the one that goes viral."

Chicago has become a national symbol of gun violence since at least 2012, when the number of homicides climbed past the 500 mark, far higher than any other U.S. city. With police initiating a number of crime-fighting measures and spending millions of dollars on overtime, the city saw the total fall closer to 400 in each of the next two years, and 2014 ended with the fewest homicides in decades. But last year the number of homicides and shooting incidents rose again.

There has been a growing concern that the rising number of shootings and homicides in Chicago, and around the country, can be linked to less aggressive policing following high-profile officer shootings, some of which were caught on camera and inflamed public outrage.

In October, Chicago Mayor Rahm Emanuel said officers are going "fetal," pulling back and second-guessing themselves for fear that scrutiny of their actions would get them into trouble.

Then in late November, the city dealt with one of the biggest crises in Chicago Police Department history — and of Emanuel's political career— sparked by the release of a video showing a white officer shooting black teenager Laquan McDonald 16 times. Officer Jason Van Dyke has been charged with murder in the shooting, police Superintendent Garry McCarthy was fired and the U.S. Department of Justice launched a civil rights investigation.

Escalante said he does not believe the McDonald video has made officers reluctant to do their jobs, point out that the department didn't have a significant drop in the number of street stops in December.