The 60 Freeway was shut down in both directions early Wednesday in the Chino area after police responded to a report of a man with a knife.
The response led to a major backup during the morning drive. Police initially responded to a report of a man armed with a knife and causing a disturbance at a Denny's.
When police arrived, the man ran onto the freeway.
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In a tweet, police said they are "dealing with a suspect" on the freeway.
"For the safety of our community, the freeway is still shut down while the investigation continues," police said in the tweet. "We appreciate your patience and will give more updates as available."
Police used a stun gun after the man walked toward a freeway work crew. He was arrested on suspicion of parole violations and resisting an officer with force.
Officers opened fire during the response, but the man was not struck by gunfire, police said. He was hospitalized with non-life-threatening injuries.
The road reopened after about two hours.
Aerial video showed about six police vehicles blocking a stretch of the road. Yellow police tape was placed across all lanes.
Some drivers were turning around on the freeway. Others were standing outside their vehicles as they waited for the road to reopen.
Drivers were being taken off the freeway at Ramona and Reservoir avenues.