Clues are surfacing about who might be responsible for a series of violent attacks on bicyclists in Minneapolis in recent weeks with chunks of concrete.

Police late Wednesday released a tally of five assaults in all since July 20, with three occurring in rapid succession Friday. Four of the victims were on bicycles, and one was in a car.

Each victim was approached by a motorist as he drove "in an erratic manner" before hurling the concrete at his intended targets, according to a statement from police.

"The suspect is believed to possibly work construction as one victim noted a yellow vest," the statement added. 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.

As for the suspect's vehicle, police describe it as an older model white Ford, possibly a Bronco vehicle or a pickup with a topper on it. One of the rear windows is missing, and cardboard or wood covers the opening.

Neither Elder nor Ethan Fawley, executive director of the Minneapolis Bicycle Coalition, considers the apparently unprovoked attacks on Friday as evidence of an escalation of tension between drivers and cyclists. Crash rates involving cyclists in Minneapolis are generally heading down, especially as drivers become more accustomed to cyclists on busy routes.

Police detailed each attack:

• July 20, 6 p.m., at 2nd Street NE. and 22nd Avenue, bicyclist seriously injured.

• Aug. 4, 5:30 p.m., at West River Parkway and Lake Street, bicyclist seriously injured.

• Aug. 7, 4:01 p.m., in the 2500 block of 11th Avenue S., motorist not injured.

• Aug. 7, 4:20 p.m., W. 41st Street and Bryant Avenue S., bicyclist slightly injured.

• Aug. 7, 4:20 p.m., W. 41st Street and Aldrich Avenue S., bicyclist seriously injured.

Among those badly hurt was 20-year-old Mackenzie Jensen, who suffered severe facial injuries Friday in the most recent assault as he was bicycling to work.

Anyone with information about any of these incidents is asked to call Crime Stoppers at 1-800-222-TIPS (8477) or the Police Department's tip line at 612-692-TIPS (8477), or send an anonymous text to CRIMES (274637) and begin the message with TIP674.

Staff writer Steve Brandt contributed to this report. Paul Walsh • 612-673-4482