By CBS3 Staff

PHILADEPHIA (CBS) — The Philadelphia Fire Department has announced funeral arrangements after the tragic loss of Lt. Sean Williamson. Lt. Williamson was killed in a building collapse following a fire in North Philadelphia over the weekend.

After placing a fire at a pizza restaurant on the 300 block of West Indiana Avenue under control on Saturday morning, Williamson and five others went back inside the building to make sure there were no hidden fires.

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An hour later, the building collapsed just before 3:30 a.m. Williamson was killed in the collapse and four other firefighters and an L&I inspector were rescued from the rubble.

A viewing will be held for Williamson at Epiphany of Our Lord Church on the 1100 block of Jackson Street on Sunday, June 26 from 6 p.m. to 9 p.m. and Monday, June 27 from 9 a.m. to 11 a.m.

A funeral mass will be held at the church on Monday, June 27 at 11 a.m. Following the mass, the Philadelphia Fire Department will stage a funeral procession beginning at Engine 59/Ladder 18/Medic 4 at 2201 W. Hunting Park Avenue.

The procession will end at Stolfo Funeral Home on the 2500 block of S. Broad Street.

The Philadelphia Fire Department is heartbroken by the loss of Lt. Sean Williamson, who provided dedicated service to our city for 27 years. Williamson died in the line of duty after a fire-damaged building collapsed in the Fairhill neighborhood on June 18.

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Fire Commissioner Adam Thiel said Lt. Williamson was one of the most experienced lieutenants on the force. He was most recently assigned to Ladder 18 in Tioga/Nicetown.

He had trained countless numbers of new firefighters, and cadet firefighters and served in the U.S. Marine Corps.

He leaves behind his mother and son.

Philadelphia Mayor Jim Kenney ordered flags be flown at half staff for 30 days in Philadelphia.

On Monday, Pennsylvania Gov. Tom Wolf ordered the commonwealth flag to be flown at half staff until sunset on Friday, June 24. It will also be flown at half staff on the day of Williamson’s funeral.

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The ATF’s National Response Team is assisting in the investigation into the origin and cause of the fire that resulted in the building collapse.