ABC News' Alex Perez, Shushannah Walshe, and Gina Sunseri report:
KILLEEN, Texas- Theodis Westbrook drove more than ten hours from his hometown near Jackson, Miss., to Killeen, Texas, to see his son Jonathan, among the first shot Wednesday when Spc. Ivan Lopez went on a rampage at Fort Hood , killing three soldiers and wounding 16 others before being confronted by a military police officer and killing himself.
"The entire drive over here, all day dodging traffic and thinking about … how different it could have been, how much worst it could have been, how much worst the news could have been and how our lives would have been changed had it gone the other way," Westbrook told ABC News, stopping to speak before reuniting with his wounded son. "It's been a harrowing experience to go through this."
Sgt. Jonathan Westbrook was shot twice in the arm and twice in the chest.
"I can't tell you how happy I am as a dad, as the parent, that I am here to celebrate with my son … and not here to go the other way," said his father.
In exclusive video of the moment the family reunited late Friday evening, Theodis and his wife Katherine gently hugged their son - so careful of his four wounds - while Theodis grateful his son is alive said over and over, "That's a big boy." Jonathan, clearly still in pain, winced while he embraced his family. Photographs shared by the Westbrooks with ABC News show Jonathan's chest and arm bandaged.
"Ever since my kids were very, very small, I was afraid that something (would) cause pain and hurt to them and I did everything in my power to prevent that," Theodis Westbrook said. "And, then when they became grown, I still worried about them getting hurt or injured out there in the world. And, for this to happen, it is the realization of the worst nightmare."
Westbrook served in Afghanistan and his father worried then, but said the pain that he suffered at the hands of a fellow soldier here is "beyond my ability to express or describe to you."
"My son was deployed to Afghanistan last year and he spent 9 months in Afghanistan," Westbrook said. "Bombs, missiles and all sorts of weapons used against him and he survived all of that and he came back here to a U.S. military installation that is secure and almost lost his life and got wounded. It is just unbelievable."
For seven hours after the shooting, the Westbrooks didn't hear from their son.
"We walked the floor, we cried, we prayed," Westbrook said, describing the hours of agony, adding "because we had no information … we allowed ourselves to think the very worst."
"It has to be bad because if it wasn't bad, then somebody would call us and let us know," he said, recounting the hours of waiting. "And since nobody had, we just fell apart … since Wednesday, we have just been to hell and back."
When they did speak, Jonathan told his family what happened. Lopez became enraged when an employee would not give him a leave of absence form, asking him to come back the next day. He returned, but this time with a gun, Westbrook told his father.
"The very first person that was hit died," Theodis Westbrook said, recounting what his son told him. "And, then the gun was turned on my son … And at that time, they began turning over tables and desks to protect themselves from any other bullets. After that, the guy left out of that particular office building and went about the campus shooting randomly at other people."
Authorities said they don't believe the shooting was premeditated, but Lt. Gen. Mark Milley, the post's commanding general, did say it was likely the result of an "escalating argument."
The reunion is one the Westbrook family will never forget and the shooting has changed this already close-knit family forever.
"I will probably tell him that I love him a little bit more often," Westbrook said, adding he is "eternally grateful, beyond description."
ABC News' Joshua Hoyos contributed to this story.