Phantom from Space

Phantom from Space is a 1953 independently made American blackandwhite science fiction film produced and directed by W. Lee Wilder from an original screenplay written by William Raynor and Myles Wilder, starring Ted Cooper, Noreen Nash, Dick Sands, and Burt Wenland. Working with most of the same crew, this was one of several early 1950s films made by Wilder and son Raynor on a financingfordistribution basis with United Artists and, on occasion, RKO Radio Pictures.

Their investigation uncovers this man is actually a humanoid creature from outer space, who has the ability to become invisible. They start a massive manhunt, causing a public panic over a radioactive invisible alien running loose.The action culminates in Los Angeles where the invisible alien has been tracked. He becomes trapped inside the famous Griffith Observatory. Now breathing heavily because his breathing gas reserves are running low, he eventually becomes visible. He is then easily shot while highup on the Griffith telescopes upper platform. Possibly because he may have only be wounded or has now run out of breathing gas reserves, he falters, and then falls to his death. ........

Source: Wikipedia