Strange noises heard in Oklahoma

This encounter occurred on march 2006 in Le Flore County, Oklahoma. Former marine David Anderson and his 12 and 9 year old sons go camping deep in a remote dense forest. While they are getting everything set up for later that night, they hear a strange, unusual call. They didn't really mind it at all. That night when the three people fell asleep they hear branches snapping and they see a huge silhouette of an ape-like creature. David Anderson described it to be taller than his Nissan Pathfinder.
He had weapons with him in the tent but he figured that one shot would not affect the creature too much anyway. A year after the first encounter David Anderson and his kids come back to the exact same camping spot despite their close call. Within 5 minutes of their time there they heard ape grunts but did not see anything in the tent. I'm not sure if they kept on camping.

Anderson,David. Holson Valley State Game Management Area, Le Flore County, Oklahoma. bigfootencounters.com. n.p. 14 Nov. 2007. Web. 1 Dec. 2011