UPDATE 4-German tycoon Adolf Merckle commits suicide

* German billionaire Adolf Merckle hit by a train

* Merckle family controls HeidelbergCement

* HeidelbergCement shares drop more than 12 pct on news

(Adds further details, suicide note)

By Markus Nagle

BLAUBEUREN, Germany, Jan 6 (Reuters) - German billionaire Adolf Merckle has committed suicide, in despair over the huge losses suffered by his business empire during the financial crisis, his family said on Tuesday.

The media-shy billionaire, whose family controls some of Germany's best-known companies, was hit by a train on Monday evening, local officials said.

"The desperate situation of his companies caused by the financial crisis, the uncertainties of the last few weeks and his powerlessness to act, have broken the passionate family entrepreneur and he took his own life," a family statement said.

State prosecutors from the southern city of Ulm said Merckle, 74, left work on Monday and died after being hit by a train near the town of Blaubeuren. He left behind a suicide note to his family, they added.