Wingsuit jumper dies after crashing into a tree in the French Alps

Alexander Polli, a skydiver and pioneer in BASE jumping, died after a wingsuit crash in the French Alps.

Polli, 31, crashed into a tree while jumping in the Couloir Ensa near Chamonix yesterday, PGHM mountain rescue officials told NBC News. Polli died at the scene, which is popular - and dangerous - for BASE jumpers.

"It's a location where there are a lot of accidents," a PGHM rescuer who gave his name only as Mercer told NBC.

The World Wingsuit League wrote on Facebook that "Alex was known for his hard-core proximity lines and that legacy continues to inspire new generations of jumpers for years to come. Besides jumping, friends from all around the world are going to miss his free-spirit energy and contagious laughter."

Polli, who held dual Italian and Norwegian citizenship, was widely known for jumps that had millions of views on YouTube. In 2013, he dropped from a helicopter through the narrow opening of Batman Cave in Montserrat, Spain, while flying at speeds of up to 155 miles per hour. The breathtaking video of the jump has been viewed more than 13 million times on YouTube.

BASE jumping consists of parachuting or flying in a wingsuit from a fixed structure or cliff, with BASE standing for building, antenna, span and Earth - the four categories from which one can jump.

Polli is the second Italian BASE jumper to die in less than a week. ANSA, the Italian wire service, reported that Uli Emanuele, who, like Polli, filmed videos that became online sensations, died Thursday in a crash at Lauterbrunnen in Switzerland.

Emanuele, 29, filmed the jump that claimed his life when he lost control after jumping from the top of one of Switzerland's Dolomite mountains. He crashed into rocks before he could deploy his parachute.