Adjectives with suffix -ed are followed by the preposition.../ Los adjetivos con sufijo -ed van seguidos de la preposiciòn...

http://grammar.ccc.commnet.edu/grammar/adjectives.htm
The -ed ending modifiers are often accompanied by prepositions (these are not the only choices):
We were amazed at all the circus animals.
We were amused by the clowns.
We were annoyed by the elephants.
We were bored by the ringmaster.
We were confused by the noise.
We were disappointed by the motorcycle daredevils.
We were disappointed in their performance.
We were embarrassed by my brother.
We were exhausted from all the excitement.
We were excited by the lion-tamer.
We were excited about the high-wire act, too.
We were frightened by the lions.
We were introduced to the ringmaster.
We were interested in the tent.
We were irritated by the heat.
We were opposed to leaving early.
We were satisfied with the circus.
We were shocked at the level of noise under the big tent.
We were surprised by the fans' response.
We were surprised at their indifference.
We were tired of all the lights after a while.
We were worried about the traffic leaving the parking lot.