Would I be terrible to leave my boyfriend after he went through something traumatic?

I have 5 kids and started dating my boyfriend back in September. Everything has been fine. He's met my kids. He's such a fun person to be around. But I'm finding out now he lied to me. About a child. He has a child and how I met him traumatized all of us. Long story short, some boy between ages 16 and 18 showed up at the door and when my bf answered it he pulled a gun on him and shot him in the foot. I was screaming and thought we were being robbed until the kid said "Hey daddy!" Luckily my kids were with their dad but I was scared and this kid wasn't saying anything else. He put a gun to my bfs head and some girl who who maybe was a girlfriend said "Babe. He's not worth it." So the kid put the gun down and acted like he was gonna walk away but then told my bf "You don't deserve this." And shot him in his genitals said fuck you dad and they left. I called 911 and my bf was screaming but yelled at me to shut up and he told the hospital he did it to himself. Completely lied and I don't think they believed him. He's not being honest with me. I asked why he hid a whole child from me, he said it's complicated and just know that anything that his son says is a lie and stuff like that. I feel like I didn't sign up for this. He's been in the hospital. I feel awful wanting to break up with him during this traumatic time but if he can't be honest with and I have children. If they're going to be put in danger being with him than I need to put them first right?

Edit: it wasn't at my house, it was at his. The kid saw me but didn't say anything to me. I was just crying on the couch. I also no I shouldn't have introduced him to my kids so soon. That was a mistake