Christians where did Luke get his information about Judas death since he wasn't there?

When I first read the bible, I had questioned this story numbers of times And no one would answer the question. Now I have read on here where a few people say, well he was probably over a ledge and the rope probably broke. But if that was true, how come in acts ACT 1:18: "Now this man (Judas) purchased a field with the reward of iniquity; and falling headlong, he burst asunder in the midst, and all his bowels gushed out." but in MAT 27:5-7: "And he (Judas) cast down the pieces of silver in the temple, and departed, and went and hanged himself. And the chief priests...bought with them the potter's field." Judas couldn't have purpose the field with the money that was given to him by the chief priests since he threw the money down and left. And I hate to be the one to say this, but the atheists are right at pointing this out. And like I posted on my questions dealing with Luke and Paul. There is something fishy about these two guys. Luke wrote the book of acts. Luke and Paul was not there during the time of Christ. So where exactly did Luke get his information from?