INQUIRER: Beau Zabel, 23, came to Philadelphia from Minnesota six weeks ago, eager to experience urban East Coast living and to become a math teacher in the city school system. He found a place to live through roommates.com in South Philadelphia near the Italian Market, and took a temporary job at the Starbucks at Fourth and South Streets.He recently updated his page on myspace.com, which proclaims his optimism: “Just waiting for life to begin.” But his life ended at about 1:30 a.m. today, when police said Zabel was ambushed as he walked home from the midnight shift at the coffee shop. He was shot once in the neck in the 800 block of Ellsworth Street and fell to the sidewalk, police said.He was pronounced dead at the scene. The motive was robbery, said Sgt. Frank Hayes of the homicide squad. No arrests were made.Zabel was the city’s 139th homicide this year, compared to 181 by this time last year.