Officers say the crime happened at around 2:20 p.m. Feb. 28 in the 400 block of Landfair Avenue in a residential area of Westwood, west of the UCLA campus.
The victim screamed and the suspect took off. A roommate called police, who then detained Evan Ryan Baldwin less than 10 minutes later near the corner of Veteran and Weyburn avenues.
The victim was not injured.
Baldwin is being held on $1 million bail.