The first happened outside Target on R Street near Loughborough Drive around 8 p.m. Friday. Officers say three teens armed with guns confronted two people who were leaving the store on their bicycles.
They demanded money and took the victims' bikes. Investigators are still searching for those suspects.
The second armed robbery happened about 10 p.m. on G Street near Alexander Avenue. Police say the victim was riding his bicycle to a gas station when he saw his friend fighting with two men.
When he tried to intervene, one of the suspects pointed a gun at his head. The other suspect then punched him and took his bike. Officers later arrested two 18-year-olds for the robbery.
They do not believe the two cases are related.