President Obama and Texas Gov. Rick Perry are headlining a Thursday afternoon memorial service at Baylor University in Waco, Texas, honoring first responders and other victims of last week’s Texas fertilizer plant disaster in nearby West.

A dozen first responders died while battling the April 17 West Fertilizer plant fire and explosion. Three others were also killed in the incident, which is still under investigation.

“Each of the men who lost their lives had stories. But the thread that bound them together was their sense of community,” Perry said. “These were volunteers. Ordinary individuals blessed with extraordinary courage.”