How to know if my teenager is bipolar

My 16 almost 17 year old started some weird behavior about 2 month ago to the point I got him drug tested because I was worried he was taking drugs. Starting off, his dad was bipolar. He passed away 9 years ago to suicide. But his didn't onset until he was in his mid 20's. He was going through horrible depression. He neglected his hygiene. Wouldn't get out of bed. Wouldn't be take a shower. He just stayed in bed watching YouTube videos on his phone. Then he would just randomly snap at me. He had gotten out of bed finally and was making breakfast. All I said was "It's good to see you out of bed. Make me a pancake too would you." He said "Why don't you make your own fucking pancake!" That's out of character. He's not a disrespectful kid. He's always been kind and had manners. But he was just having random bursts of anger. Then when I thought he was going doing drugs because his behavior was so weird I went through his phone and he was texting his best friend a bunch of nonsense talking about how he's figured everything out. That humanity is unhappy and needs to be free and he's figured out how to free everyone. Nothing he was saying made sense to the point even his 16 year old friend is telling him maybe he needs to get help because nothing he's saying makes sense and he's worried. This all seems like manic behavior. I am going to try to take him to see a doctor and see what they say but does this sound like bipolar. At the moment he seems normal but just yesterday he was bad on his setting everyone free nonsense.

@Kimberly he's not talking about killing people. From what I could pick up from his random gibberish he thinks humanity is being enslaved by technology and he's the one meant to destroy technology to set everyone free. That's what I a picking up from his weird texts