Sto:lo Nation president Joe Hall says no threats were made before shots were fired at the nation's administration building at 1:37 p.m. Monday.
"It's very disturbing," he said, but fortunately no one was injured.
He said police asked staff to remain in the building at 7201 Vedder Road until their investigation was finished.
"I don't know any more than that," he said.
Initial reports said a single bullet was fired through a second-floor window in a building that houses child protection services. The bullet was found inside.
"At this point, there is no indication this was targeted," said RCMP spokesperson Corporal Tammy Hollingsworth.
"If this was an accidental discharge of a firearm we are asking that person to contact us."
Chilliwack RCMP Serious Crime Section and the UFVRD First Nations Policing Unit are continuing to investigate.
Anyone with information is asked to call the Chilliwack RCMP at 604-792-4611 or Crime Stoppers at 1-800-222-8477 (TIPS).
Watch www.theprogress.com for more information as it becomes available.