The California teachers' pension fund still hasn't shaken off its investment in gun maker Bushmaster, more than two years after the mass shooting at Sandy Hook Elementary School.

And now the teachers are mad. California teachers are planning a protest at the fund's meeting on April 2.

The pension fund CalSTRS had vowed to sell off all its investments in firearm companies after the elementary school shooting in December 2012. Within months, it sold off shares of Sturm Ruger (RGR) and Smith & Wesson (SWHC).

Ironically, the fund has still not been able to divest off its investment in Freedom Group, which makes the Bushmaster assault rifle used by the shooter who killed the 26 Sandy Hook students and educators.

That's because CalSTRS doesn't directly invest in Freedom Group. It is an investor in three funds managed by private equity firm Cerberus Capital. Those funds have investments in the Bushmaster manufacturer Freedom Group, also known as Remington Outdoor.

"Cerberus has been earnestly trying to find a buyer but so far has not been able to sell the holdings," said CalSTRS spokesman Mike Sicilia.

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Now teachers are planning a campaign to pressure CalSTRS to get rid of its investment.

"As teachers and parents, we see the havoc that these guns bring to our community, our family and our loved ones," said Joshua Pechthalt, a Los Angeles high school teacher for 20 years and president of the California Federation of Teachers. "So whatever it takes, we want our money divested from gun manufacturers."

Besides protests at the fund's annual meeting in Sacramento, they will also release a documentary which features interviews with teachers who question why their money is invested in Cerberus.

"Teachers understand first hand the impact of gun violence on students," said Robert Greenwald, who directs the documentary.

CalSTRS is one of the largest funds in the country, managing $190 billion of California teachers' pensions.

School teacher Pechthalt said the fun should just get rid of the investment even if it takes a hit.

"If it means a slight loss, so be the case," he said. "I think we're not weighing [what's] financially beneficial, while there's a child being shot in one of our schools."