An explosion in a Bronx drug lab killed a firefighter Tuesday morning, sources said. Emergency responders were called to the home on W. 234th St. near Irwin Ave. for a gas leak at 6:22 a.m., officials said. After they arrived, firefighters discovered a drug lab, sources said.The house exploded about 7:30 a.m., collapsing its roof and sending smoke billowing over the neighborhood.“When it exploded, 3 blocks away me and my son were in my apartment and the entire building shook,” Instagram user advocateofwordzw wrote.An FDNY battalion chief wounded by the blast was rushed to the hospital but could not be saved, sources said.(nydailynews.com)…[+]