At least 18 children and three adults were killed in a shooting at a Texas elementary school on Tuesday, multiple US media reported. “I was just briefed by the Texas Rangers, 18 children have passed on, and three adults,” Texas State Senator Roland Gutierrez told several US media outlets including CNN. Gutierrez added that the suspect’s grandmother was in critical condition. CNN earlier reported the suspect had shot his grandmother before heading to the school, citing multiple law enforcement sources. The death toll makes the Robb Elementary School shooting the deadliest since 20 Sandy Hook el…