The shocking tweet students saw: "Buckeye Alert: Active Shooter on campus. Run Hide Fight. Watts Hall. 19th and College."
UPDATE: "[L]aw enforcement officials told NBC News he was an 18-year-old Ohio State student, a Somali refugee who was a legal permanent resident of the United States."
The motive was unknown, but officials said the attack was clearly deliberate and may have been planned in advance.The attacker didn't use a gun but a car and a knife.