(AP) — A Wisconsin woman and her adult son were killed in separate traffic crashes just hours apart in a Milwaukee suburb, police said Monday.

Mary J. Moore, 45, died after she was struck by a vehicle, on a street in West Allis. A friend was speeding her son, Thomas M. Olson, 22, to the hospital to see her when he struck three parked cars and overturned, West Allis Deputy Chief Charles Padgett said. Olson was killed in the crash about 5:30 a.m. Sunday.

Padgett said Olson knew his mother had been hit, but he wasn’t sure if Olson knew she had died.

“It’s emotional. We want to get there fast and sometimes disregard our safety,” Padgett said. “I use it to remind people that regardless of the circumstances, be aware of the speed.”

The driver of the car OIson was riding in was arrested on suspicion of driving while intoxicated. He and two other passengers suffered non-life-threatening injuries.

Moore was hit as she lay prone in the street. A motorist following the car that struck her told police it looked as though the vehicle hit a speed bump, according to the Milwaukee County Medical Examiner’s report. The witness did not realize that it was a person until getting closer, the report said.

Padgett said Moore had been drinking before she was hit, but it’s not clear how much. An autopsy on her body was expected to be done Monday.

The driver that hit Moore drove off, but officers later found and arrested the person they believe is responsible. That driver may also have been drinking, authorities said.

“In my 24 years (of law enforcement), I’ve seen a lot of strange things, but don’t specifically remember a case like this,” Padgett said.