PRINCE GEORGE'S COUNTY, Md. (DC News Now) -- Police in Prince George's County are actively investigating after a man boarded a county school bus, that was carrying elementary school students. Just after 2 p.m., the Prince George's County Police Department (PGPD) received a call from a person who saw a man board the bus. They were immediately dispatched and stopped the bus at 2:09 p.m., determining the three students on board were all safe. Preliminarily, investigators said the bus driver picked up the man and drove him to D.C. before returning to the county, all while the students were still on board. Initial information indicates the driver knew the man and is possibly related to him. Early voting off to a strong start in West Virginia eastern panhandle The man was no longer on board by the time police stopped the bus. Investigators believe the man was involved in a fight with someone in the 3900 block of Suitland Road shortly before boarding the bus. It appears he may have had a gun during the dispute, but did not bring it on the bus, PGPD noted. The gun was found near where the dispute happened. PGPD officers are still working to find the man who was driven into D.C. This is a developing story.