SEOUL, South Korea (CBS SF) — U.S. Ambassador to South Korea Mark Lippert was slashed by a man in a violent attack during in Downtown Seoul.

According to witnesses, Lippert was about to give lecture at the time when the attacker reportedly came after him with a knife.

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Pictures on South Korean TV showed the ambassador bleeding from his face and blood over his clothes.

Lippert suffered a cut on his face requiring 80 stitches and a deep gash to his arm, but his injuries were not life threatening. President Barack Obama called the ambassador after the attack to wish him a speedy recovery.

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The suspect was immediately arrested. He reportedly was upset about a joint military drill involving the U.S. and South Korea. Witnesses said he yelled “South and North Korea should be reunified.”

“The assailant has been arrested and is in the hands of local authorities, and we’re deeply appreciative to the Korean National Police,” said Robert Ogburn of the U.S. Embassy in South Korea.

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Lippert graduated with a bachelor’s degree from Stanford in 1997 and earned his master’s degree the following year. He was named ambassador to South Korea last year.