More than 70 people were shot during a violent weekend in Chicago, including a seven-hour period Sunday when 40 people were wounded, The Chicago Tribune reported Monday.

According to data compiled by the newspaper, 11 people were killed and 61 people were wounded between 3 p.m. Friday and 6 a.m. Monday. The victims’ ages ranged from 11 to 62.

Between midnight and 7 a.m. Sunday, 40 people were shot and four were killed, WGN reported. In seven incidents, three or more people were shot, the television station reported. In one shooting, eight people were wounded, including four teenage girls, WGN reported.

Chicago police Patrol Chief Fred Waller said Sunday that in some cases, gang members were using large summer crowds as targets.

“They take advantage of that opportunity and they shoot into a crowd, no matter who they hit,” Waller said at a news conference.

As of Friday, at least 1,700 people have been shot in Chicago this year. That number is fewer than the past two years but higher than in other recent years, the Tribune reported.