The claim is true because multiple reports published in June 2022 say Ken Paxton told a radio host that he would explain the Uvalde victims’ deaths by saying that God has a plan, although “part of a plan by God” is a paraphrase rather than the most precise wording.
Ken Paxton said the Uvalde shooting was part of a “plan” by “God.”

Texas GOP Attorney General Ken Paxton on the Uvalde massacre: 'God has a plan' - Alternet.org
Source: alternet.org
Key Evidence
The Houston Chronicle and San Antonio Express-News reports describe Paxton telling a conservative radio host that he believed God always has a plan for the children killed in Uvalde.
Salon, Raw Story, and other June 2022 reports give substantially the same account.
The exact phrase “part of a plan by God” is best treated as a paraphrase of his reported “God has a plan” remarks, not necessarily as a verbatim quotation.
What the Evidence Shows
In June 2022, shortly after the May 24, 2022 shooting at Robb Elementary School in Uvalde, Texas, Paxton was asked what he would say to parents whose children had been killed. The available reports consistently describe him as saying that God has a plan or that there is a purpose in what God does.
The wording in the input is therefore substantially supported, but it compresses the reported statement. The sources generally attribute to Paxton the wording “God has a plan,” rather than a direct statement that the shooting itself was explicitly “part of a plan by God.” Some headlines use the stronger formulation that the massacre was part of God’s plan, while the underlying descriptions indicate that Paxton was discussing divine purpose and what he would tell grieving parents.
The evidence comes from several contemporaneous reports, including the Houston Chronicle and San Antonio Express-News, as well as secondary outlets that reproduced or summarized the interview.x.comx.comPG Kroeger on X: "'Paxton was impeached by his own party for bribery and... is a much later social-media post and is not independent confirmation; it repeats the allegation in abbreviated form.