Stemen, who reportedly injected the semen, appeared to try to help the woman figure out what happened after the attack.
"It felt like a bee sting didn't it?" he allegedly asked her.
Police received an anonymous tip on Tuesday naming the man as the culprit.
They then found the syringe in the driver's side door of his car, local media reports.
A judge has ordered him to be held without bail.
Police continue to investigate and believe there could be additional victims.
It is not clear whether the two know each other.
"This investigation is extremely active; additional charges may be applicable," police said on Twitter.