MINNEAPOLIS — Minneapolis police are trying to figure out who is hurling chunks of concrete at random people.

There have been five assaults since July 20, with three in rapid succession Aug. 7, according to a press release.

Four victims were on bicycles, and one was in a car. Two bicyclists were seriously injured and two were slightly injured. The person in the car was not injured.

“The suspect is believed to possibly work construction as one victim noted a yellow vest,” according to a police statement. He is believed to be in his 20s, police said. Police spokesman John Elder said earlier that the driver was wearing a glove and was believed to have thrown with his left hand.

According to police, each victim was approached by a motorist as he drove “in an erratic manner” before throwing concrete.