In the first robbery, a 14-year-old South San Francisco boy was riding his bike in the park at about 7:15 p.m. on July 5 when another teenager confronted him, police said.
The boy was forced off his bike, and suspect took it and rode off, police said.
Investigators later gave the victim a photo lineup and he picked out 18-year-old Luis Gomez as the teen who had attacked him and taken his bike, police said.
The stolen bike was recovered and Gomez was arrested the next day. Gomez was booked into San Mateo County Jail on robbery charges, and is being held on $50,000 bail.
On July 9, a Daly City man was walking through the park at about 8:30 p.m. when three men wearing black hoodies and tan pants assaulted him and stole his cellphone, according to police.
He was taken to a hospital to be treated for cuts and bruises on his face, police said.
No arrests were made in that case, and no suspects have been identified.
Anyone with information is asked to contact South San Francisco police at (650) 877-8900.