短语讲解：

1. Police in the U.S. arrested a man Thursday in connection with a mass shooting in South Carolina Wednesday.

in connection with 与…有关，连同
例句：He was in detention in connection with the bribery affair.
他因与贿赂事件有牵连而被拘留了。

2. Twenty-one year old Dylann Storm Roof is suspected of killing nine people at an African-American church in the city of Charleston.

be suspected of 被怀疑患有…，被怀疑（做）…
例句：He is suspected of employing trickery.
他有弄虚作假的嫌疑。