A 26 year old Aitkenvale man's in police custody after allegedly firing a rimfire rifle on the banks of the Ross River this morning at about 7.
A woman saw the agitated man with what looked to be a gun, and shortly after heard a loud bang, and phoned police.
Police have arrested a man matching her description on a bike, and found the gun a short time later.
He is yet to be formally charged.
Officers say there were several calls reporting shots around the time, and they're hoping more people will come forward with information.
If you can help in the investigation, contact Policelink 131 444.