Cloud, next time use a real word, if you can find one.

There was trouble from the Grundi. One of them damaged the spaceship by hurling a rock at it. The astronauts couldn't figure out what the Grundi had to gain by their hostile act. Was it just vandalism, done out of sheer spite? Or perhaps not everyone on Mars was happy to see the Earthlings return.
The Martian police brought in five Grundi for questioning. Like all Grundi, they sometimes told the truth and sometimes lied. The suspects each made three statements, two of which were true and one of which was false. And the guilty one was revealed.
1. Zum said:
I am innocent.
I have never uysed a rock to destroy anything.
Tset did it.
2. Uk said:
I did not do the damage.
The Earthman's vehicle is on Grundi space.
Yan is not my friend.
3. Pala said:
I am innocent.
I never saw Yan before.
Tset is guilty.
4. Tset said:
I did not throw the rock.
Yan did it.
Yum did not tell the truth when he said I did it.
5. Yan said:
I am innocent.
Uk is guilty.
Pala and I are old friends.
Who was the culprit?