De Castro's broke through the windshield, and his neck was heavily bruised.
The incident is still a blur in his mind.
"I didn't remember that I pass out," he said.
De Castro's doctors found a splintered bone in his neck, and they say he is lucky the injury didn't leave him paralyzed.
But what concerns De Castro most is not what could have happened to him, but rather what could still happen to someone else.
"I have my uniform. I have my cap with 'crossing guard' (on it). I thought she would stop," he said. "If they can hit a crossing guard, how much more (neglectful will they be) of the kids?"
De Castro has worked as a crossing guard for more than a dozen years, and this is not the first time he has witnessed such disregard for this crosswalk by a driver. The year after he started working as a guard, a driver hit his 14-year-old daughter in the exact same crosswalk.
She has fully recovered since, and these two accidents only drive De Castro to work harder to keep others safe.
"They should be observant of what's happening, especially (in) the cross walk. They should be more concerned," he said.
Now, instead of walking kids, Des rests with his medicine close at hand. Just standing up is enough to make him dizzy.
Despite his condition, De Castro says his heart is full, thanks to the outpouring of support from his Salmon Bay family.
"I know in my heart that these kids appreciate what I'm doing," he said.
"It's really the talk around school, you know. 'How is Des? Is he going to be okay?'" said Salmon Bay volunteer coordinator Sharon Feliciano. "And to see the kids rally around him is really heartwarming."
Even as he recovers, De Castro, who lives across the street from the school, is keeping an eye out the window, waiting to get back to his post.