 -- Police are investigating whether two officer-involved shootings in St. Louis and its suburb of Ferguson are linked to protests over the shooting death of 18-year-old Michael Brown.

The first shooting happened shortly after 9 p.m. Saturday when a Ferguson police officer was conducting a business check at the city's community center, according to a statement from the St. Louis County Police Department.

When the officer saw two men behind the building, they began running away, said St. Louis County Police Chief Jon Belmar. As the officer ran after the men, one "spun toward the officer armed with a handgun, and fired shots at the officer," hitting him once in the arm. The officer shot back.

"There is no indication at this time that the suspect was struck by return gun fire from the officer," read the county police department's statement.

The officer was treated at a local hospital.

Belmar said he did not think the shooting was related to recent protests in Ferguson, where Brown was shot and killed by a police officer last month.

In a second shooting on I-70, an off-duty St. Louis police officer was driving home after midnight Sunday in his personal car when shots were fired by someone inside a passing Dodge Charger, said police. Investigators aren't sure whether the shooting was a targeted incident or a random act of violence.

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The officer's car was hit "numerous times," according to police. He suffered minor injuries from broken glass and was treated at a local hospital.

Investigators don't believe the shootings are related.

Tensions between police and residents in the St. Louis suburb have continued since Ferguson police officer Darren Wilson shot and killed Brown on Aug. 9. There were weeks of protests, including some incidents of looting and clashes between demonstrators and police.

Earlier this week, Ferguson Police Chief Thomas Jackson apologized to Brown's family, who told The Associated Press that they wanted him fired.

A state grand jury is considering whether Wilson should face criminal charges and the Department of Justice is also investigating.