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Five schools kept children off playgrounds and nervous commuters changed their routes Monday as authorities searched for a suspect in more than 20 random, unsolved shootings in southeastern Michigan.

Oakland County Sheriff Mike Bouchard urged the public to be vigilant, saying wide eyes probably were more critical than changing a daily routine.

"If you see something, say something. We'd rather check out 10 false things than miss one real," Bouchard told The Associated Press. "This is not going to slow us down. We're going to find this person."

No one has been hurt, and no shootings have occurred since Thursday. But a task force with officers from nine departments raised the number to 22 shootings after getting fresh reports in the region, more than 30 miles northwest of Detroit.

The shootings have happened in four counties. Most involve cars near Interstate 96, though authorities said one occurred while a man was taking out his trash. In another incident, a woman said the rear window on her car was shattered. Ten of the 22 shootings were in Wixom in Oakland County.

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Tipsters told police the gunman appears to be a man in his 30s, and authorities have released a drawing of a possible suspect with close-cropped hair and stubble on his cheeks and chin. While the shootings appear to be random, police are investigating them as a pack.

The Walled Lake school district felt compelled to lock doors at five schools in Wixom and keep kids inside at recess on a beautiful fall day, though there was no evidence schools are a target. It's not clear how long the policy will be in effect.

"We want all our students and families to feel safe. These are precautionary measures," spokeswoman Judy Evola said.

Josephine Salem, 47, said she's very concerned about her 12-year-old daughter.

"She runs cross-country after school, and that's less than maybe a quarter-mile from where the school is," Salem said. "The kids have to run outside, and a stray bullet, you know -- I think about it a lot."

A police car was parked at Wixom Elementary School as buses pulled up to take students home for the day. The officer had a view of students and the road, where several shootings occurred less than a mile away last week.

The shootings were a hot topic on morning drive-time radio shows with listeners calling or texting their plans to avoid I-96 in certain areas. Casey Smiles tweeted that she was taking a different route to Ann Arbor from the Lansing area to avoid the "scary" shooter.

The shootings occurred in Oakland, Livingston, Ingham and Shiawassee counties, from last Tuesday through Thursday.

"You can never be too careful, obviously," Oakland County Undersheriff Mike McCabe said. "Until this guy or suspects are found, people need to be aware of their surroundings. There is nothing wrong with taking precautions."