PHILADELPHIA -- The National Guard confirmed Thursday that Francis Straub, 24, of Philadelphia, was among the men killed in Iraq on Tuesday.

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Straub is the seventh member of the Pennsylvania National Guard killed in Iraq in less than four days.

Not only was Straub killed on Tuesday, his grandmother died Wednesday night. Straub's brother said that he is in total shock.

"At first you let it out. Then you can't believe he's gone," Sean Straub said.

Sean Straub is trying to come to grips with the loss of his brother "Frankie." Francis Straub died when his unit's Humvee was attacked in Beiji Tuesday night. They were investigating an incident.

"They encountered a well-coordinated attack, initiated by an improvised explosive device," said Lt. Commander Marc Ferraro, of the Pennsylvania National Guard.

Francis Straub was one of four children who grew up in the West Kensington area of Philadelphia. His siblings said that he always wanted to be in the military.

"He was a chess guy. He was one of the best in chess. He was also one of the top in his place with sheet metal," Sean Straub said.

A preliminary investigation showed that the explosives used in the insurgent attack were detonated when Straub's rapid response team passed by, creating craters as large as 11 feet and 7 feet wide.

"The (explosives) consisted of 25 to 50 pounds of high explosives. We do not know whether it was artillery rounds or a land mine," Ferraro said.

"Loved ones are being lost every day. He's a hero. He died for his country. What for? I don't know, let's ask Bush," Sean Straub said.

On Wednesday, it was announced that three other members of the same National Guard unit were killed in Iraq -- Spc. Gennaro Pellegrini Jr., 31, a Philadelphia police officer and promising boxer; Pfc. John Kulik, 35, a firefighter from Jenkintown; and Pfc. Nathaniel DeTample, 19, a recent graduate of Pennsbury High School in Fairless Hills.