Shut off engine now it won't start

[Cordus]

I have a 2002 Tahoe. 5.3 l in it. I turned car off normally, went inside for 5 mins came out and car needed jumped. Did this and vehicle wouldn't start. All I heard was a clicking noise so I bought a new battery, and new starter. All I get is a loud single click. I can see starter engage, teeth go into the flywheel, but it's like the flywheel won't budge. Tahoe started fine, ran fine, then I shut it off normally and now this. Has anyone ran into this problem. HELP.....

 

[jmplants_1]

Check or wire connectors from battery down to starter

 

[Cordus]

I replaced starter wire also. Cleaned all grounds. Added an extra ground just because lol. I can see starter engage, lock into teeth on flywheel but won't budge after that. I cannot seem to turn engine by hand either. Which is odd because it ran fine I just shut truck off and went inside to grab something.

 

[Cordus]

Lost with this. Anybody run into this?